Self-checking burner safety control apparatus



May 11, 1954 H. HANSON SELF-CHECKING BURNER SAFETY CONTROL APPARATUS Filed Jan. 14. 1949 INVENTOR HENRY L HANSON L i! infill! ATTORNEY Patented May 11, 1954 SELF-CHECKING BURNER SAFETY CONTROL APPARATUS Henry L. Hanson, I/Iinneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 14, 1949, Serial No. 70,946

Claims.

The present invention is concerned with an electronic fuel burner control apparatus and more particularly with that type of an apparatus which will automatically shut the fuel burner down in the event there is a flame failure and which will maintain the fuel burner inoperative should any portion of the control apparatus not be operating properly.

In present day fuel burner controls, it has been found that electronic devices can be utilized to improve the operation of the burner that is being controlled by responding quickly to flame failure and providing an over-all circuit that is generally more universal and easily controlled. By incorporating electron discharge devices in the present invention, it is possible to utilize a single relay in controlling the operation of the controlled fuel burner and it is further possible to arrange the electrical circuits so that this relay will be deenergized upon a flame failure and will be maintained deenergized if there is a false indication of flame or any part of the control apparatus is not operating properly. This is accomplished by utilizing electron discharge devices of the thermionic type and charging and discharging resistance and capacitance networks associated with these discharge devices in accordance with the operating condition of the burner and the operating conditions of the control apparatus itself.

It is therefore an object of the present invention to provide a control apparatus for a fuel burner which employs a single relay which is adapted to energize the burner, and providing, for energizing this single relay, an electron discharge device which is rendered operative only when the associated components are operating properly I and which device will deenergize the single relay should the burner fail to operate.

Another object of the present invention is to provide a control apparatus employing an electronic means for energizing a single relay which is adapted to complete an energizing circuit to the burner and connecting this energizing electronic means with said relay so that said reiay cannot be energized unless a predetermined voltage exists on the input of the electronic means.

Still another object of the present invention is to provide a burner control apparatus which includes an electronic control for a single relay where the electronic control is operative to re cycle the control relay a predetermined number of times in the event that a flame is not established at the burner. y

Astill further object of the present invention is to provide an improved control apparatus which utilizes a single relay for energizing a control for a burner and a flame detector which will render the control inoperative if the ignition means fails or will maintain the control inoperative if the control apparatus is not operating properly.

A. still further object of the present invention is to provide an electronic control apparatus for a fuel burner which has a single relay adapted to energize the fuel burner and further has an electronic ignition apparatus which is operative while the single relay is energized and there is no flame detected at the burner.

These and other objects of the present invention will be understood upon a consideration of the following specification, claims, and drawings or" which:

The single figure shows the present invention as employed with an oil burner.

Referring to the single figure, it will be seen that an appropriate fuel burner I0 has been provided. For indicating when there is a demand for operation of the burner [0, a thermostatic device I i may be provided and this may be located in any suitable space wherein a temperature is being controlled. When the thermostatic device i i indicates the need for operation of the burner it, the thermostatic device will close an electrical circuit associated with the controls of the subject invention which are located in a housing indicated'generally by the numeral 52. The circuits within the housing I 2 are operative to complete an energizing circuit to the burner it and to supply energy to an appropriate ignition transformer 53. As soon as the burner flame appears at the nozzle of the burner Hi, this flame will be detected by a suitable flame detecting device it which may be in the form of a photoelectric cell.

Located within the housing it are the control circuits which render the burner IS operative upon a demand for heat and check the burner operation and these control circuits may be seen to include a main power transformer it which has a primary winding it, connected to a suitable source'of power, not shown, and a plurality of secondary windings indicated by the numerals El, iii, it and it. The secondary winding 19 has a pair of taps thereon indicated by the numerals 2! and 22 while the secondary winding 20 has a tap thereon indicated by the numeral 23.

For completing an energizing circuit to the burner iii, a relay 25 has been provided and this relay comprises, a relay winding 28 and a plural ity of switch blades 21, 28, 29, 30, and 3|. The

switch blades 21, 28, and 29 are normally biased, by means not shown, into engagement with contacts 32, 33 and 34 respectively. Switch blades and (H are normally biased out of engagement with their associated switch contacts 35 and 3B. When the relay becomes energized and the switch blades move into their energized position, the switch blades 21, 28, and 29 will move into engagement with their associated contacts 31, 38, and 39 respectively.

A discharge device 40 is used to control the energization of the relay 25 and this discharge device may be seen to consist of an anode M, a control electrode 42 and a cathode 43 which is heated to be electron emissive by a suitable filament type of heater 44. Connected in current controlling relation with the discharge device 45 are a condenser 45 and a resistor 46. A further resistor 41 is associated with the input of the discharge device 48 and the condenser 45. A cur rent limiting resistor 48 is associated with the filament heater circuit 44.

The flame detector may be seen to consist of a suitable electron discharge device 56 which device has an anode 5I, a control electrode 52, and a cathode 53 which is heated to be electron emissive by a suitable filament type of heater 54. Associated with the input of this discharge device i a biasing resistor 55 and a filter network comprising a resistor 56 and a condenser 5'1. A further condenser 58 is provided for use in the circuit of the photoelectric cell I4. Located in the output of the discharge device 55 are a pair of electrical networks in a form of parallel connected resistors and condensers. comprises a resistor EI and a condenser 62 while the other network 63 comprises a resistor I54 and a condenser 65.

For controling the energization of the ignition transformer It a further electron discharge devic IE3 is provided and this device would preferably be of the gaseous type and will include an anode 'I I, a suppressor grid I2, a control electrode I3 and a cathode I4 which is heated to be electron emissive by a suitable filament type of heater, not shown. Associated with the input to this discharge device iii are a pair of resistors I5 and I6. Located in the output circuit of this discharge device, in addition to the transformer I3, is a safety cutout device 18 and this device may be seen to include a heater I9, a bimetallic ele ment 80, and a pair of switch contacts SI and 82. The heater 19 is operative when energized for a predetermined length of time to warp the bimetal 89 toward the right so that the contacts BI and 82 will separate. A reset actuator 83 is provided for moving the contacts BI and 82 back to the closed position after there has been a safe ty shutdown.

Operation In considering the operation, it will first be noted that the apparatus as shown upon the drawing is in the deenergized position with the thermostatic device I I not caling for burner operation and with the burner It and ignition transformer I3 deenergized. Further, in considering the following assume the alternating current secondary windings of transformer I5 are, for a particular half cycle, phased as shown upon the drawing. When the apparatus is in the shutdown position, the main control discharge device 40 and the flame detection discharge device 50 are eifectively nonconducting since their filament heaters are not receiving full voltage from the secondary transformer winding I8. This A first network is because the limiting resistor 48 is connected in the series circuit to the filaments of the two discharge devices. This filament circuit may be traced from the upper terminal of secondary winding I8 through conductor I06, resistor 48, conductor I02, filament heater 44, conductor I03, contacts BI and 82 of the safety cutout device "I8, conductor I04, filament heater 54, and conductor I05 back to the lower terminal of secondary I8. The current flowing in the last traced circuit is sufiicient to keep the filament heaters 44 and 54 in a partially energized condition so that upon a call for burner operation the filament heaters will not have to change temperature over a wide range, which change tends to deteriorate the filament heaters more quickly than would ordinarily occur if the filaments were left partially energized continuously.

As soon as the space wherein is located the thermostatic device I I begins to cool, the contacts of the thermostat will close and the closing of these contacts will be effective to shunt out the current limiting resistor 48 in the filament heater circuit for discharge devices 40 and 50. This shunt circuit may be traced from the left hand side of resistor 48 through conductor I55, thermostatic device II, and conductor IIi'I back to the right hand side of resistor 48. This shunting of the current limiting resistor will mean that full voltage or" th filament secondary winding I8 will be applied to the heaters 44 and 54 and the temperatures of these heaters will increase to a point where the associated cathodes 43 and 53 respe tively will becom electron emissive.

As soon as the filament heater 54 heats the cathode 53 to be electron emissive, there will be a current flow through the discharge device 50. When the phasing of the secondary transformer IQ is such that the lower terminal of the secondary is positive with respect to the upper terminal, the current flow through the discharge device 5! may be traced from the tap 22 on secondary I9 through conductors I I I) and I I I, resistor 6 I, anode 5i, cathode 53, conductor I I2, conductor H3, switch arm 29, contact 34, and conductor H4 to the tap 2! and the secondary i9. With the current flowing in the last traced circuit, there will be a direct current voltage built up across the condenser 62 since the current flow through the discharge device 50 and the resistor 6i will be unidirectional.

The voltage drop on condenser 62 will be such that the upper terminal is positive and the lower terminal is negative. The charge that has been built up upon the condenser I52 is used to control the potential of the control electrode 42 of the discharge device as and this voltage is applied to the control electrode 42 and cathode 43 in a circuit that may be traced from the upper terminal of condenser 62, through conductor II5, switch contact 32, switch blade 21, resistor 41, to the control electrode 42 and from the control electrode 42 through resistor 46 to the cathode 43, from the cathode 43 through conductor IIS, switch arm 28, contact 33, and conductors II? and H8 to the lower terminal of condenser 62. If the voltage on condenser 62 is sufiiciently positive on this upper terminal with respect to its lower terminal, a positive voltage will be built up across the condenser 45 on the input of discharge device 40 since this condenser is effectively connected in parallel with the resistor 46. The charge on this condenser 45 will be such that the upper terminal is positive and the lower terminal is negative. If the voltage on the condenser 45 is sufiiciently positive on its upper terminal, there will be sufiicient current passing through this discharge device 40 to energize the main control relay 25. The energizing circuit for the relay 25 may be traced from the upper terminal of secondary I! through conductor 129, relay winding 26, anode 4I, cathode 43, and conductor I 2| back to the lower terminal of secondary H. The relay 25 is so designed that the relay can become energized only when the current flow through the discharge device 49 is such as to indicate that the control electrode 42 is slightly positive with respect to the cathode 43.

As soon as the relay 25 has become energized, an energizing circuit is completed to the burner is and this circuit may be traced in the input power line I25 through conductor I26, switch blade 3|, switch contact 36, conductor I21, and burner It back to the other input power line I28.

Also energized when the relay 25 becomes energized is the ignition circuit of the subject apparatus. The ignition circuit is normally arranged so that when the relay 25 is deenergized the ignition circuit will be inoperative. This will be understood when it is noted that the control electrode 13 of discharge device I6 is normally connected to a point of the power source which is negative with respect to the cathode 14 when the discharge device has its anode 'I'I connected to a positive point in the power source. This will be seen when the anode circuit for the discharge device 73 is traced and this may be traced from the upper terminal of secondary 23 through conductor 133, heater i9, ignition transformer I3, conductor it i, anode I I, cathode l4, and conductor E32 to the tap 23 of secondary 29. It will be noted that the control electrode I3 is connected through the resistor I6 and conductor I33 to the lower terminal of secondary 29. Before considering how the discharge device I9 becomes energized upon the energization of the control relay 25, it is also necessary to note that the discharge device 53 is effective to charge the condenser 65 and network 63 so that the upper terminal of the condenser 65 is positive with respect to its lower terminal. This will be understood when the half cycle of the alternating current on secondary winding I9 is such that the upper terminal of secondary I 9 is positive with respect to the lower terminal. When the secondary I9 is so phased, it is possible to have a current flow from the upper terminal of secondary I9 through conductor I35, resistor 64, conductor I36, anode cathode 53, conductors H2 and H3, switch blade 29, switch contact 34, and conductor H4 to the tap 2| on secondary i9. Since the current flow in the last traced circuit will be unidirectional there will be a voltage drop across resistor 64 so that the condenser 65 will be charged so that the upper terminal is positive with respect to the lower terminal.

Going back to the ignition circuit again, energization of the relay 25 will cause the discharge device it to become conductive if the proper voltages exist in network 63 on the output of the flame detection discharge device 50.

When the relay 25 becomes energized an electrical circuit may be traced from the control electrode E3 of discharge device I0 through the resistor i5, conductor I38, switch blade 30, switch contact 35, conductor I39, network 63, conductors 533 and i3! and conductor I32 to the cathode i i. This last traced circuit, neglecting the effect of the charge on condenser 65 and network 33 is essentially a voltage divider network connected across the lower portion of the secondary winding 20 between tap 23 and the lower terminal of secondary 20. The voltage on the control electrode in this circuit is such that the control electrode will still be sufficiently negative with respect to the cathode I4 so that the discharge device ID will not become conductive upon the positive half cycle or conductive half cycle of the secondary 26. If, however, there is a positive voltage existing in the network 63, this positive voltage when added to the alternating current voltage in the voltage divider network is effective to bring the control electrode I3 into the range where the discharge device In will fire or conduct on every positive half cycle of the secondary 23. When the discharge device does fire there will be a current flowing in the anode circuit that was traced above and this will mean that current will be flowing through the ignition transformer I3 and there will be a resultant sparking across the electrodes of the ignition transformer and this sparking will ignite the fuel that is coming from the burner III.

When the relay 25 becomes energized the network 33 in the flame detection discharge device circuit is reconnected to the input of the main control discharge device 49 so that now the negative terminal of condenser 62 is connected to the control electrode and positive terminal of condenser 62 is connected to the cathode 43. This circuit may be traced from the upper terminal of condenser 62 through conductor H5, switch contact 38, switch blade 28, conductor H6 to cathode 43 and from cathode 43 through resistor 46, to the control electrode 42, from control electrode 42 through resistor 41, switch blade 2?, switch contact 31, conductor I40, and conductor H9 to the lower terminal of condenser 62. At the same time that this last traced circuit comes into eifect, the cathode 53 of the flame detection discharge device 50 is connected to the lower terminal of secondary I9 and this circuit may be traced from the cathode 53 through conductors H2 and H3, switch blade 29, switch contact 39, and conductor I4I to the lower terminal of secondary I9.

With the cathode 53 now connected to the lower terminal of secondary I9, the anode circuit for the discharge device 59 may be traced from the tap 22 through conductors H0 and III, network 60, anode 5L cathode 53, conductors I i2 and H3, switch blade 29, switch contact 39, and con ductor I4I to the lower terminal of secondary 29. A further anode circuit for this discharge device may be traced from the upper terminal of secondary I9 through conductor I35, network 33, and conductor I36 to the anode 5| and from there through the last traced circuit to the lower terminal of secondary I9. When the discharge device is so connected to the secondary i9, when the upper terminal of the transformer I3 is positive with respect to the lower terminal, there will be current flow in the last traced circuits and the direct current potential built up across the condensers of netwonks 6i] and 63 will remain of the same polarity as they were previously when the cathode 53 was connected to tap 2|. With the network 60 reconnected to the input of discharge device 40, the charge on corn denser 62 will be such as to tend to bias the control electrode 42 negative to a point where the relay 25 will become deenergized. The time that it will take for this to occur will be dependent upon the size of the resistor 47 which is in the charging circuit for the condenser 45 and also upon the size of the resistor 46 which is in parallel with the condenser 45. Normally the presence of flame at the burner will be detected and the charging of the condenser 45 in a negative direction on the control electrode end will be stopped. This will be understood when the operation of the flame detector photocell upon the flame detection discharge device 50 is considered below.

Normally, when no flame is detected on the discharge device 50, the above traced circuits with respect to the discharge device 50 are normally operative as the control electrode 52 is biased to be slightly positive with respect to the cathode 53. This is because the condenser 58, resistor 56 and parallel connected condenser 51 and resistor 55 form a voltage divider network between the anode connection of the discharge device and the cathode 53 as connected to secondary l9. With the control electrode 52 slightly positive with respect to the cathode, on the positive half cycle of the alternating power source, the current flow will be as traced above. When flame is detected by the photoelectric cell l4, a direct current charge is built up across the condenser 58 since the photocell i4 is an asymmetrically conducting device when exposed to the light of the flame. The charge on the condenser will result because of the fact that there is a current flow flowing from the tap 22 through conductor i it, condenser 58, conductor I45, the anode of photocell I4, cathode of photocell l4, conductors 146 and H3, switch blade 29, switch contact 35, and conductor i4! back to the lower terminal of secondary IS.

The charge built up upon the condenser 53 will be such that the lower terminal is negative and the upper terminal is positive and this charge will be effective to bias the control electrode 52 to be negative with respect to the cathode 53. This will mean that the current fiow in the discharge device 55 will no longer exist and there will be no further charging of the condensers 52 and 55 in the networks 60 and 63. When there is no longer a direct current potential existing across the network Gil, this network will not be tending to bias the control electrode 42 of discharge device 4ii to be negative and therefore the control relay will remain energized. When there is no longer a direct current charge existing across the network 63, there will be no direct current voltage maintaining the control electrode '53 of the ignition discharge device 10 positive with respect to the cathode i4 and this will mean that the ignition discharge device l will no longer be supplying an energizing voltage to the ignition transformer 13.

The apparatus described thus far is now operating in its normal manner with the ignition device not energizing the ignition transformer l3, the photocell detecting the presence of flame and maintaining the flame detection device 50 inoperative and the potential between the oathode 43 and control electrode 42 of the main control discharge device such as to maintain the relay 25 energized and the burner operative.

As soon as the thermostatic device II is no longer indicating a need for further burner operation, the contacts will separate and this will remove the shunt around the current limiting resistor 48 in the filament heater circuit for filament heaters 44 and 54. With the shunt removed from the current limiting resistor 48 the filament heaters 44 and 54 will begin to cool and will cool to a point where the heaters will no longer be effective to heat the cathodes 43 and 53 to be electron emissive. When the cathode 43 is no longer electron emissive the current flow through the discharge device 40 will drop to a value which will no longer be suflicient to maintain the relay 25 energized and therefore the contacts 21 through 3| will move to their deenergized position. When this occurs, the energizing circuit to the burner ID will be opened with the opening of switch blade 3| from contact 35. Thus, the apparatus will be shut down and the components will return to the positions shown upon the drawing.

In considering the operation upon a flame failure, first assume that a normal operating cycle has started with sufficient voltage on the network 55 being effective to cause the main control discharge device 40 to become operative to energize the relay 25. It will be recalled that when the relay 25 becomes energized an energizing circuit is completed to the burner iii and the ignition electron discharge device it will be effective to energize the ignition transformer it. Further, with relay 25 energized, the connections of the control electrode 42 and cathode 43 are reversed upon the network (iii so that now the condenser 52 is tending to charge the condenser 45 to be negative on the control electrode side. This circuit may be traced from the lower terminal of condenser 52 through conductor lit, conductor i421, switch contact 3?, switch blade 22', resistor 47, to condenser 45, on a control electrccle side thereof, and from the other side of the condenser 15 through conductor i It, switch blade 28, switch contact 38, conductor H5 to the upper terminal of condenser 82.

If a flame is not established within a predetermined time, the condenser 45 will assume a charge which will he sufliciently negative with respect to the cathode that the control electrode will decrease the current flow through the discharge device 43 below the point necessary to maintain relay 25 energized. The time that it will take for this to occur will be dependent upon the size of the resistor 41 which is connected in series with the charging circuit of condenser 45 and the size or the resistor 45 which is connected in parallel with the condenser 45. When the relay 25 becomes deenergized the condenser 45 on the input of discharge device 49 is reconnected across the network iii) so that the con denser will tend to be charged so that the control electrode side is positive with respect to the cathode side. Again, the time that it will take for this positive voltage to appear upon the condenser 45 will be dependent upon the size of the resistor 4"; and resistor 45. After a predeter mined time the condenser 45 will have charged sufficiently positive on the control electrode side so that the discharge device will become conductive again and will have suificient current flowing therethrough to energize the relay 25. If flame is not established by the ignition device within a predetermined time, the apparatus will again be shut down since the condenser 45 will be reconnected so that it will tend to charge negative on th control electrode side with respect to the cathode side.

Again, after a predetermined time, the condenser will be recharged so that it will be positive and the control relay 25 will become energized. Each time that the relay becomes energized, the ignition device "it will be effective to apply an energizing voltage to the ignition transformer and at the same time will be applying an energizing voltage to the heater 79. This heater 19 9. is so designed that it is capable of storing heat between the succeeding attempts to establish a flame at the burner and, after a predetermined number of times, the heat stored in the heater [9 will be sufficient to move the bimetal toward the right and the contacts 8| and 82 will separate. When they have separated, the filament heater circuit to heaters 44 and -4 will be broken and therefore the discharge devices as and so will. become deenergized and the apparatus will be completely shut down. After the heater '59 has cooled sufliciently, it is possible to depress the actuator 83 and move the contacts 3i and 32 to the closed position. As soon as the circuit is closed the filament circuit will be completed and the discharge devices as and 53 will be effective to go through their normal operating cycle in the manner described above. If a flame is not established upon the recycling of the relay a predetermined number of times the apparatus will again shut down in the manner described above.

As soon as the fault causing non-appearance of the flame at the burner has been eliminated, the apparatus will go through its normal operating cycle as described above under Operation.

Component check It is necessary in the apparatus to provide as much safety as is possible to insure that the apparatus does not operate the burner when the control apparatus is not functioning properly. Thus, upon the starting up of the apparatus, it will be seen that it is necessary that the filament circuit for filaments 44 and 54 be intact. If not, it is impossible for the filaments to heat the associated cathodes to be electron emissive. Further, it will be realized that upon the starting cycle that it is impossible to energize the control relay 255 until such time as there is a positive voltage applied to the control electrode 42. Thus, if there is a short between the control electrade 42 and the cathode 43 of the main control discharge device 46, it would be impossible to energize the relay 25 because there would not be sufficient current flowing through the discharge device 43. Further assuming that the circuits for. the discharge device 40 are functioning properly, since a positive voltage must be applied to the control electrode 42, it will be seen that there must be a positive voltage originating in the network as in the output of the discharge device 5 3. This positive voltage on the network Eli will. be of sufficient magnitude only when the control electrode 52 is slightly positive with respect to the cathode 53. Thus, when the control relay 25 is deenergized and the cathode 53 is connect-ed to the tap 2!, it will be seen that the control electrode 52 is effectively connected to a point in the power source or secondary H! which is of a potential slightly positive with respect to the cathode connection 2! since the condenser 58", resistor 53', and resistor 55' and condenser 57 are connected between the anode connection 22 and cathode 53. This, as explained above, is essentially a voltage divider across the corresponding portion of the power source so that the control electrode will be slightly positive. If the control electrode 52 should be short circuited to the cathode 53, the positive voltage existing across the network 63' will not be sufficient to energize the main control relay 43'.

In the event that there is a short circuit between the anode 5| and the cathode 53, it will be noted that an alternating current biasing voltage is applied to the condenser 45 which will-- 10 be suflicient to maintain the control electrode 42 negative with respect to the cathode 43. The control electrode 42 connection to the secondary winding I9, when this short circuit exists, may be traced from the control electrode 42 through resistor 47, switch arm 21, switch contact 32, conductor H5, and conductors Ill and Hi) to the tap 22 of secondary !9. The cathode connection for cathode 43 may be traced from the cathode 43 through conductor H6, switch blade 28, switch contact 33, conductors H'! and H8, anode 5!, cathode 53, conductors H2 and H3, switch blade 29, switch contact 34, and conductor H4 to tap 2! on secondary l9. With this connection, and the secondary windings l1 and I3 both phased so that their upper terminals are positive with respect to their lower terminals, it will be noted that the control electrode 42 is connected to a point that is negative with respect to the cathode connection at tap 2|. Thus, the discharge device 40 cannot become energized.

Should a similar short circuit occur between the anode 4| and the cathode 43 of the main control discharge device 40, the discharge device would no longer be asymmetrically conductive and since the relay 25 is of the direct current type, this relay will not become energized as there will be no direct current flowing in the anode circuit of the discharge device.

Should a short circuit occur between the control electrode 52 and anode 5| of the flame detection discharge device 50, the above traced circuit wherein the control electrode 42 was connected to a point on transformer l9 which was negative with respect to tap 22 will apply and, while the voltage on this circuit will be less than that originating when there was a direct short circuit between the anode 5i and cathode 53, this alternating current voltage will be sufiicient to maintain the discharge device 40 nonconductive. This circuit may be traced from the control electrode 42 through the resistor 41', switch blade 21, switch contact 32, and conductors H5, l H and H0 to the tap 22. The cathode connection in this situation may be traced from the cathode 43 through conductor H6, switch blade 28, switch contact 33, conductors H1 and H8, anode 5|, control electrode 52, parallel connected resistor 55 and condenser 5! to conductor H2 and from there to conductor H3, switch blade 29, switch contact 34, and conductor H4 to tap 21. Since the condenser 58 and resistor 56 form a voltage divider with the parallel connected resistor 55 and condenser 51, it will be seen that the actual voltage existing upon the cathode 43 will not be that which is directly upon the tap 2| but a point that lies between the tap 2| and the tap 22 on secondary 19. As mentioned above, this voltage will be sufiicient to maintain the control electrode 42 negative with respect to the cathode 43 and there will be no current flow through the discharge device 40.

Further, if there is any fault in the ignition circuit, the apparatus will shut down'after it has recycled a predetermined number of times as was explained above under a flame failure. If there should be any fault in the ignition circuit which would tend to cause an increase in the amount of current flowing in the anode circuit of the discharge device 10, as would occur upon a short circuit across the electrodes of the ignition transformer l3 or upon a short circuit between the anode H and control electrode 14, there would be an increased amount of current flowing through the heater 19 and therefore this heater 1i will cause the apparatus to shut down much sooner than would ordinarily occur should the apparatus fail to detect the presence of flame at the burner.

Thus it can be seen that the apparatus will not become operative to energize the burner unless all components in the apparatus are in a condition to operate safely.

Conclusion From the foregoing it can be seen that I have provided an electrical fuel burner control apparatus which will be rendered ineffective if the associated ignition means fails, if the flame fails, or if any component of the apparatus fails to operate in its normal manner. While I have shown specific embodiments of my invention, it is to be understood that it has been for illustrative purposes only and I therefore intend to be limited solely by the scope of the appended claims.

I claim:

1. Burner control apparatus comprising in combination, a source of power, a relay, said relay having a plurality of switch contacts two of which are adapted to complete an energizing circuit to the burner when said relay is energized, a first electron discharge device connected to said source of power, an input circuit for said first discharge device, an output circuit for said first discharge device, said first discharge device be ing energized upon a demand for burner operation, means connecting said relay in the output circuit of said first discharge device to be energized by the current flow in said output circuit upon a demand for burner operation, flame detecting means responsive to the presence or absence of burner flame, a second electron discharge device connected to said source of power, an in-- put and an output circuit for said second discharge device, means connecting said detecting means to the input circuit of said discharge device, an electrical impedance network connected in the output circuit of said second discharge device and adapted to have a voltage thereacross oi": a first value indicative of the prcsence of a flame at the burner or of a second value indicative or the absence of flame at the fuel burner, a capacitor, means connecting said capacitor to the input circuit of said first discharge device to control the current flow in the output circuit of said first discharge device in accordance with the voltage across said capacitor, means including switch contacts of said relay which are closed when said relay is deenergized and including said network for charging said capacitor in a first sense when said relay is deenergized, said first sense being of a polarity to cause operation of said first discharge device and thereby energize said relay upon a demand for burner operation and further means including switch contacts of said relay which are closed when said relay is energized and including said network for charging said capacitor in a second sense, said capacitor being charged in said second sense only so long as said flame detecting means responds to the absence of burner flame to maintain said voltage of said second value across said network, said second sense being of a polarity to render said first discharge device ineffective to maintain said relay energized after a predetermined time period, said capacitor when charged alternately in said first and second sense by voltage across said network causing recycling of said relay and the 12 burner in attempting to establish flame at the burner.

2. Burner control apparatus comprising in combination, a source of power, a relay having a plurality of switch contacts a first of which is adapted to complete an energizing circuit to the burner when said relay is energized, relay energizing means adapted to energize said relay upon a demand for burner operation, electronic ignition means including a grid controlled rectifier having a control grid, means including a second of the switch contacts of said relay to render said ignition means effective when said relay is energized, flame detecting means, an electron discharge device connected to said source of power, a control circuit for said discharge device including said flame detecting means, an output circuit for said discharge device, an electrical impedance network connected to said output circuit, said impedance network thereby being adapted to have a voltage thereacross of a first value indicative of the presence of a flame or of a second value indicative of the absence of a flame, means connecting said network to the control grid of said grid controlled rectifier to control said electronic ignition means in accordance with the presence or absence of flame, and safety cutout means having an actuator in circuit with said ignition means, said cutout means having means to render said relay energizing means ineffective when said ignition means has been energized for longer than a predetermined time.

3. Burner control apparatus comprising in combination, a source of power, a relay including means for completing an energizing circuit to the burner when said relay is energized, a first electron discharge device having a control electrode and an anode and cathode, means con necting said relay in circuit with said anode and cathode, means including said source of power adapted to render said first discharge device operative upon a demand for burner operation, ignition means, a second electron discharge device, an input and an output circuit for said second discharge device, means connecting said ignition means to said output circuit, burner flame detecting means, a third electron discharge device having a control electrode and having an anode and cathode, a first electrical impedance network connected in circuit with the anode and cathode of said third discharge device, a second electrical impedance network connected in cir cuit with the anode and cathode of said third discharge device, means connecting said flame detecting means to the control electrode of said third discharge device, said first and second networks thereby being adapted to have a voltage thereacross of a first value indicative of the presence of a flame or of a second value indicative of the absence of a flame, means connecting said first network to the control electrode of said first discharge device and said second network to the input circuit of said second discharge device to cause recycling of said relay and said ignition means when a burner flame is not established, and safety cutout means having an operator connected in circuit with said ignition means, said cutout means having means to render said first discharge device inoperative after said ignition means has been recycled a predetermined number of times.

4. Burner control apparatus, comprising in combination, a source of power, flame detection means, an electron discharge device connected to said source, said discharge device having a control electrodt Connected to said flame detection means and: having an anode andcathode, an electrical impedance-network connected in 1 series with said anode and cathode, said network therefore normally having a voltage-thereacross of a first value indicative of the presence of flame or of. a second value indicative of absence of a burner flame, a relay, means controlled by said relay adapted to energize the. burner when said relay. is energized, electronic means connected to said source for energizing said relay upon a demandfor burner operationand including a further discharge device having. a control electrode to control the current flow therethrough, said electronic means. having a main current circuit including said discharge device and said relay to energize said relay in accordance with the voltage applied to said control electrode, first means electrically connecting said network to the control electrode of said further discharge device so that upon demand for heat said further discharge device will initiate energization of said relay to energize the burner if the voltage across said network is of. said second value, and second means rendered operative upon a demand for burner operation for electrically connecting said network to the control electrode of said further discharge device so that said further discharge device will maintain said relay energized only for a period of time unless the voltage across said network changes from said second to said first value upon said flame sensing means sensing the presence of flame within said period of time, said first means maintaining said further discharge device inoperative to energize said relay if the voltage across said network does not change from said first to said second value.

5. Burner control apparatus comprising in combination, a source of power, a relay, said relay having a plurality of switch contact pairs, a first pair of which are adapted tocomplete an energizing circuit to the burner when said relay is energized, a first electron discharge device connected to said source and having an anode, a cathode and a control electrode, means adapted to render said first discharge device operative upon a demand for operation of the burner. means connecting said relay in circuit with said anode and cathode to thereby energize said relay when there is a demand for burner operation, burner flame detecting means, a further electron discharge device connected to said source, said. further discharge device having a control electrode connected, to said flame detecting means and having an anode and cathode, an electrical. ire-- pedance network connected in series with the anode and cathode of said further discharge device to cause a voltage to exist across said net work which is of a first value indicative of the presence of flame at the burner or of a second value indicative of the absence of flame at the burner, means including a second pair of relay switch contacts which are closed when relay is energized connecting said network to the control electrode of said first discharge device for rendering said first discharge device ineiicctive when the burner flame fails, and means including a third pair of relay switch contacts which are closed when said relay is deenergized con necting said network to the control electrode of said first discharge device for maintaining said. first discharge device ineffective to energize said relay unless the voltage on said network lies within said second value indicative of the absence of flame.

6. Burner control apparatus comprising in combination; a sourceof. voltage, flame sensing means, electronic flame detection apparatus connected tov said; source and comprising an electron discharge device havinga control electrode connected tosaid flame sensing means andhaving an anodeand cathode, an electrical impedance network, circuit means connecting said impedance network in. series circuit with said anode and cathode, said network, normally having a voltage thereacross of: a first value indicative of the presence. of flame or of a second value indicative of the absence; of aburner flame, a relay, means including said relay adapted to energize the burner. when saidrelay is energized, electronic means connected to said source; for energizing said relay upon a demand; for burner operation, said electronic means including a further discharge devicewhose current flow is controlled by the voltage on acontrol electrode thereof, means electrically interconnecting the control electrode of said further discharge device and said network so that said electronic means will maintain said relay energized only for: a period of time unless the voltage across said; network changes from said second to said first value upon said flame sensing means sensing the presence of flame withinsaid period of time, and means interconnecting said electronic means and said network so that when said first voltagevalue exists across said network said electronic means will not energize said relay.

7. Burner control apparatus comprising in combination, a relay, said relay having a plurality of. switch contacts two of which are adapted to complete an energizing circuit to the burner when said-relay is energized, means including an electron discharge device having main electrodes and a control electrode, means connecting said relay in circuit with. said. main electrodes to be energized when there is a demand for burner operation, a source of power, burner flame detecting means, a. further electron discharge device connected to said source of power and having main electrodes, an input circuit for said. further discharge device including: said flame detecting means, an. electrical. network, means connecting said electrical network. in. series with the main electrodes of said further discharge device, said network comprising a parallel connected resistor and condenser and adapted to have a voltage thereacross of a first magnitude indicative of the presence. of: fiame at the burner or of a second magnitude indicative of the absence of flame at the: burner, a second resistor, a second condenser, means connecting. said second resistor and said second condenser to the controlelectrode of said first discharge device in current controlling relation to said device, and means including certain of the switch contacts of said relay for connecting said network to said second resistor and said second condenser in one manner when said relay is energized and in another manner when said relay is deenergized, said last named means together with said condensers and resistors rendering said first discharge device inefiective ii there is a failure of the burner flame when said relay is energized, said last named means together with said condensers and resistors maintaining said first discharge device ineffective if said further discharge device is not operating properly or a flame is present when said relay is deenerized.

8. Burner control apparatus comprising in combination, a source of power, a relay for completing an energizing circuit to the burner when said relay is energized, energizing means for said relay including an electron discharge device connected to said source and having a control electrode, said device being operative upon a demand for burner operation, a main current flow circuit for said discharge device, means connecting said relay in said main current flow circuit, electronic ignition means normally rendered effective by said relay when energized, burner flame detecting means, a further electron discharge device connected to said source, an input circuit for said further discharge device including said flame detecting means, a first and a second electrical impedance network, a current flow circuit for said further discharge device including said first and second impedance network connected in circuit therewith, said first and second network thereby being adapted to have a voltage thereacross of a first magnitude indicative of the presence of a flame or of a second magnitude indicative of the absence of a flame, and means connecting said first network to said control electrode in current controlling relation to said first discharge device and said second network to said electronic ignition means to render said first discharge device inoperative if flame is not established and to render said ignition means inoperative if flame is established at the burner.

9. Burner control apparatus comprising in combination, a source of power, flame sensing means, an electron discharge device having an anode and cathode, an input circuit for said discharge device including said flame sensing means, an electrical impedance network, circuit means connecting said network in series with said anode and cathode, said network thereby being adapted to have a voltage thereacross of a first value indicative of the presence of a flame at the burner or of a second value indicative of the absence of a flame at the burner, a relay, a second electron discharge device energized upon demand for burner operation, means connecting said second device to said source, a control circuit and a current circuit for said second discharge device, means connecting said relay in said current circuit so that said relay will be energized upon a demand for burner operation, means including said relay connecting said network to said control circuit in current controlling relation to said second electron discharge device when said relay is energized so that said relay will be maintained energized only for a period of time unless the voltage across said network changes from said second to said first value upon said flame sensing means sensing the presence of flame within said period of time, and means including said relay when deenergized connecting said network to said control circuit in current controlling relation to said second discharge device for checking operation of said detecting means to insure that the voltage across said network is of said second value indicative of the absence of a flame at the burner prior to energizing said relay.

10. Burner control apparatus comprising in combination, an alternating source of power, a relay including means adapted to complete an energizing circuit to the burner when said relay is energized, electronic means connected to said source, said electronic means comprising an electron discharge device having an anode and cathode and having a control electrode, means connecting said relay in circuit with said anode and cathode, flame sensing means, a network having a resistor and capacitor therein, means including said flame sensing means for producing a voltage across said network which is either of a first value indicative of the presence of flame or of a second value indicative of the absence of flame, first circuit means controlled by said relay connecting said network in a first sense to said control electrode of said discharge device when said relay is deenergized so that said discharge device is conductive only when said voltage is of said second value, said network maintaining said first discharge device inoperative to initially energize said relay if the voltage thereon indicates the presence of flame when said relay is deenergized, time delay means, and further circuit means including said time delay means and controlled by the relay for connecting said network to said control electrode in a second sense when said relay becomes energized such that said discharge tends to become sufliciently non-conductive to deenergize said relay after a period of time if said voltage remains at said second value due to the failure of said flame responsive means to sense the presence of flame.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,136,256 Sweet Nov. 8, 1938 2,170,497 Gille Aug. 22, 1939 2,299,501 Schneider Oct. 20, 1942 2,304,641 Jones r Dec. 8, 1942 2,313,943 Jones Mar. 16, 1943 2,368,893 Spangenberg et a1. Feb. 6, 1945 2,370,847 Dempster Mar. 6, 1945 2,406,185 Aubert Aug. 20, 1946 2,537,293 Peterson Jan. 9, 1951 2,610,677 Lange Sept. 16, 1952 

